The typical conventional intervertebral fusion device is formed of a hollow cylindrical body having a perforated periphery, and bone graft, as exemplified by the device disclosed in the U.S. Pat. No. 4,501,269, and the BAKTEM interbody fusion system disclosed in the U.S. Pat. No. 5,015,247. The interbody fusion system comprises a rigid hollow cylindrical body containing bone graft. The rigid cylindrical body can not be adjusted in relation to the relative position of vertebrae so as to suit the intervertebral space. With a view to overcoming such a drawback as described above, this inventor of the present invention discloses an adjustable intervertebral fusion device in the U.S. Pat. No. 5,423,817. The adjustable intervertebral, fusion device is found to be defective in design in that it is rather time-consuming to implant the device, and that a relatively large incision must be made to facilitate the implanting of the device, thereby resulting in the prolongation of the post-operation healing process of the patient.